Evaporator for a Refrigerator and Method for the Production Thereof

ABSTRACT

A method for producing a heat exchanger, a) a coolant pipe and a blank are provided; b) a bead that is made of a plastic adhesive is placed between the coolant pipe and the blank so as to extend in a manner that is adapted to the shape of the coolant pipe; and c) the bead located between the coolant pipe and the blank is compressed.

The present invention relates to an evaporator for a refrigeratorcomprising a blank, a coolant pipe and a layer of adhesive connectingthe coolant pipe to the blank as well as a method for producing such anevaporator.

An evaporator of this type and a method for the production thereof areknown from DE 199 38 773 A1. In the known production method, ameander-shaped bent pipe is held pressed against a blank and theintermediate spaces between the meanders of the pipe are filled with anadhesive. This adhesive can comprise expanded PU foam or pourablethermosetting plastic. A foam is particularly advantageous as adhesiveif the evaporator is to be installed as a so-called cold-wallevaporator, i.e. the evaporator is embedded between an inner containerof the refrigerator and a thermal insulation layer surrounding the innercontainer and heat exchange is nevertheless desirable only via thesurface of the blank facing the inner container but not via its rearside bearing the coolant pipe. Potting using a non-foamed thermosettingplastic requires a considerable expenditure of material and is thereforecostly.

It is also known to secure the coolant pipe on the blank using adouble-sided adhesive tape attached between the two. In this technique,however, the adhesive tape impedes heat exchange between the coolantpipe and blank and thus impairs the efficiency of the evaporator.

Known from DE 102 18 826 A1 is an evaporator in which the coolant pipeis secured on the blank using a bitumen film which is laid on the blankand coolant pipe, heated and pressed so that the plastic bitumenmaterial penetrates as a result of the heating into the gusset formedbetween the blank and the coolant pipe and provides a large-areaadhesive bond between the two. With this technique, however, it isdifficult to ensure that the air is completely expelled from the gussetsso that remaining air pockets impair the heat exchange and can thusresult in fluctuating efficiencies of different heat exchangers.

It is the object of the present invention to provide a method forproducing a heat exchanger or a heat exchanger which can be producedusing such a method which ensures efficient and reproducible heatexchange between the coolant pipe and supporting blank of the coolantpipe by simple means.

The object is firstly achieved by a method comprising the steps of claim1.

By placing the adhesive bead having a profile adapted to the profile ofthe coolant pipe between the coolant pipe and the blank, it is ensuredthat large-area contact between said adhesive and the coolant pipe onthe one hand and between said adhesive and the blank on the other handcan be produced using a small amount of adhesive, via which intensiveheat exchange takes place between coolant pipe and blank. As a result ofcompressing the bead between the coolant pipe and the blank, theadhesive is expelled from the immediate contact area between pipe andblank so that optimal heat transfer is possible at this location.

The adhesive is preferably applied to the coolant pipe before thecompression since this ensures that the bead comes to lie over its totallength between the coolant pipe and the blank.

During compression of the bead, the coolant pipe is preferably flattenedat the same time in order to thereby enlarge the region of directcontact between the coolant pipe and the blank or to keep the thicknessof the adhesive layer on both sides of the contact region as small aspossible and to make the surfaces of the coolant pipe and blank wettedby the adhesive as large as possible.

A butyl rubber is particularly preferable as adhesive. This material isdistinguished by an extremely low water absorption and permeability andthus prevents moisture from collecting at the interfaces between theadhesive and the pipe or the blank and impairing the coherence andtherefore the thermal conductivity of the evaporator by freezing. Inaddition, by using butyl rubber with its good heat conduction propertiescompared to other adhesives, good heat transfer is produced between theblank and the coolant-carrying pipe. The good adhesive properties of thebutyl rubber also ensure a very strong bond between the coolant-carryingpipe and the supporting blank connected to the pipe which is used torelease cold, so that the pipe is securely and permanently joined to theblank and can be subjected to high mechanical loading. The food-safeproperties of butyl also make it possible to use the heat exchanger inthe user access region but particularly as an evaporator in the interiorof a refrigerator or freezer. By using butyl rubber as adhesive, bothflat heat exchangers such as so-called plate evaporators or rear-wallliquefiers and also three-dimensional heat exchangers such as so-calledbox evaporators and C-shaped evaporators as well as so-called coilevaporators can be produced with good manufacturing success on a largescale.

Another important advantage of this material is that it can be loadedimmediately after application. It is not necessary to wait for thematerial to cure after compression so that the residence time of theevaporator in a press used for this purpose can be kept short and theproductivity of the press is accordingly high.

FIG. 1 is a perspective view of a heat exchanger according to theinvention, for the example of an evaporator; and

FIGS. 2-5 each show a schematic section through parts used to producethe evaporator or the finished evaporator in various phases ofproduction.

The evaporator shown in perspective view in FIG. 1 is composed of a flatblank 1 made of aluminum sheet on which a coolant pipe 2 also consistingof aluminum is arranged in a meander shape. Blank 1 and pipe 2 are heldtogether by butyl rubber which extends between pipe 2 and blank 1 onboth sides of a line at which pipe 2 and blank 1 are in contact with oneanother.

FIG. 2 shows the coolant pipe 2 and the blank 1 in a first stage of theproduction of the evaporator, cut in a vertical plane to a rectilinearsection of the meander-shaped pre-formed pipe 2. Three sections throughthe pipe 2 can be seen in the figure; these are circular and aconnecting pipe bend 4 can be seen between two thereof. A nozzle 5 movesalong the coolant pipe 2 and is about to apply a bead 6 of butyl rubber.

In the stage in FIG. 3 the application of the bead 6 is ended and thecoolant pipe 2 together with the bead lies in grooves 8 of a pressingdie 7, whose profile is matched to the meander shape of the coolant pipe2. The cross-sectional shape of the grooves 8 approximately correspondsto half of an ellipse, the cross-sectional area of the complete ellipsecorresponding to that of the coolant pipe 2.

FIG. 4 shows the evaporator after compressing blank 1, bead 6 andcoolant pipe 2 between the pressing die 7 and a pressing stamp, notshown which is pressed from above against the blank 1. As a result ofthe pressing pressure, the cross-section of the coolant pipe 2 isflattened to an ellipse which fills the cross-section of the groove 8.The rubber of the bead 6 is expelled in the lateral direction so thatblank 1 and coolant pipe 2 come into direct contact in a narrowstrip-shaped contact zone 9 extending over the entire length of thecoolant pipe 2. Gussets 10 formed between the blank 1 and the pipe 2 onboth sides of the contact zone 9 are filled with the rubber 3 of thebead 6 and thus form two rubber strips which extend to the right and tothe left of the coolant pipe 2 over its entire length.

FIG. 5 shows the finished evaporator after removal from the pressing die7.

The butyl rubber creates a secure loadable bond between blank 1 andcoolant pipe 2. The high thermal conductivity of the rubber compared toother sealing or adhesive materials also allows efficient heat exchangebetween those surface regions of blank 1 and pipe 2 which are not indirect contact with one another. Since the gussets between the blank 1and pipe 2 are free from air inclusions, the cooling performance of theevaporator according to the invention is exactly reproducible.

1-10. (canceled)
 11. A method for producing a heat exchanger comprisingthe acts of: a) preparing a coolant pipe and a blank; b) placing a beadof a plastic adhesive having a profile matched to a profile of thecoolant pipe between the coolant pipe and the blank; and c) compressingthe bead between the coolant pipe and the blank.
 12. The methodaccording to claim 11, wherein the act b) includes the adhesive beingapplied to the coolant pipe.
 13. The method according to claim 11,wherein the act a) includes bending the coolant pipe is in a meandershape.
 14. The method according to claim 11, wherein the act c) includesthe coolant pipe having a flattened shape.
 15. The method according toclaim 11, wherein the adhesive is a butyl rubber.
 16. The heat exchangeraccording to claim 16, wherein the heat exchanger includes at least oneof an evaporator and a liquefier.
 17. A heat exchanger for arefrigerator, the heat exchanger comprising: a blank; a coolant pipe;and a layer of adhesive which joins the coolant pipe to the blank,wherein the adhesive layer extends in a strip shape along the coolantpipe.
 18. The heat exchanger according to claim 17, wherein the adhesivelayer forms two strands on both sides of a contact zone between thecoolant pipe and the blank.
 19. The heat exchanger according to claim17, wherein the coolant pipe has a flattened cross-section.
 20. The heatexchanger according to claim 17, wherein the adhesive is a butyl rubber.21. The heat exchanger according to claim 17, wherein the heat exchangerincludes at least one of an evaporator and a liquefier.